The present invention relates to a comprehensive control system and, more particularly, to a system for accepting a variety of signals, processing those signals, and generating signals operative to control a variety of devices. The processing and generating of these signals can be performed by the system, or, optionally, by an external computer, or, as a further option, by the system working together with an external computer.
Various attempts have been made to automate factory machinery and other devices. Such automation generally requires the sensing of inputs and the generation of appropriate outputs. With the advent of computers, it has generally been found desirable to have one or more computers performing this control function. However, most computers are not built to interface directly to factory machinery. For example, factory machinery may provide outputs in such forms as relay closures, thermocouple voltages, or line-voltage signals, and accept inputs such as relay closures or medium-voltage signals, while computers are designed to work with communication protocols such as RS-232 and Ethernet. There exist many systems for interfacing between computers and industrial machinery, however, they are lacking in the flexibility required to allow a system designer to easily assemble a control system, with off-the-shelf components, that provides precisely the desired types of inputs and outputs in a small space and at low cost. Further, it is desirable to be able to quickly repair a control system when components fail, and without having to maintain a large stock of replacement parts.
Factories tend to be electrically noisy environments, with frequent switching of large loads such as motors and heaters. Such electrical noise can be disruptive or damaging to computer systems. Furthermore, the skill levels of factory workers are varied, with the attendant risk that accidental connections could damage sensitive equipment. It is thus desirable that inputs to factory control systems be protected from noise and incorrect connections. Optical isolation is particularly desirable, providing a high level of safety for personnel and equipment.
In setting up and maintaining a factory automation system it is preferable that the system be as simple as possible. Thus, it is desirable that such a system be modular, and, preferably, that the addressing scheme by which a computer or other data processor selects individual inputs and outputs be automatically configured.
Because much of the interface circuitry for various types of inputs or outputs is similar, it is economical to have a generic computer interface capable of accepting a variety of input or output devices, referred to herein as “submodules”, with the submodules including specialized circuitry for each particular type of input or output. Such a generic computer interface, operative to accept submodules, can be incorporated within the computer, or can take the form of a device inserted into the computer, such as a circuit board having a standard interface, such as, for example, PCI, cPCI, ISA, PMC, VME or PC-104, to the computer, or a device connected to the computer via a standard communications port, such as, for example, RS-232 or Ethernet, or any other suitable device operative to connect the computer to submodules.
There is thus a widely recognized need for, and it would be highly advantageous to have, a modular control system capable of interfacing a wide variety of inputs and outputs, and capable of interfacing to a wide variety of computer communication protocols, or, optionally, to provide self-contained computational capability.